Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$152.30	10.823%	$168.7834	$168.78	$168.80	$168.80
Purchase #2	$79.44	3.585%	$82.2879	$82.29	$82.30	$82.30
Purchase #3	$234.61	10.143%	$258.4065	$258.41	$258.40	$258.40
Purchase #4	$203.90	7.457%	$219.1048	$219.10	$219.10	$219.10
Purchase #5	$21.29	5.110%	$22.3779	$22.38	$22.40	$22.40
Purchase #6	$239.56	13.830%	$272.6911	$272.69	$272.70	$272.70
Purchase #7	$78.31	3.281%	$80.8794	$80.88	$80.90	$80.90
7 purchase totals =	$1,009.41		$1,104.5310	$1,104.53	$1,104.60	$1,104.60